Appendicitis CT Reporting: Checklist and Complete Report Examples

What an appendicitis CT report should answer

A CT report for suspected acute appendicitis should answer three questions clearly: Was the appendix visualized, do the findings support acute inflammation, and is there a complication or alternative diagnosis? This guide focuses on adult abdominopelvic CT performed for right lower quadrant pain. Imaging pathways for children, pregnancy, and other clinical settings should follow patient-specific and local guidance.

The ACR 2022 Right Lower Quadrant Pain criteria address imaging that can assess appendicitis as well as gastrointestinal, urinary, and gynecologic alternatives. The 2025 World Society of Emergency Surgery (WSES) Jerusalem guideline emphasizes interpreting diagnostic imaging alongside clinical risk assessment. This article focuses on describing CT findings when CT has been performed; a report template alone does not establish the clinical diagnosis.

Clinical safety note: Appendiceal diameter alone is not diagnostic. Assess calibre, wall, luminal contents, and surrounding findings together. Do not call an equivocal appearance normal or definite appendicitis while uncertainty remains.

Systematic review checklist

1. Technique and coverage: Record intravenous contrast use, scan range, motion, and any limitation.
2. Find and follow the appendix: Trace it from the cecal base; state whether it is fully or partly seen, including the tip when possible. Describe an atypical position.
3. Appendix itself: Report the outer-to-outer short-axis diameter, wall thickness/enhancement, and luminal contents, then explain the combined pattern. Do not use one measurement as a stand-alone threshold.
4. Adjacent tissues: Assess periappendiceal fat stranding, localized fluid, cecal-base change, and the adjacent terminal ileum.
5. Stone and gas: Localize an appendicolith, intraluminal gas, extraluminal gas, or an extraluminal appendicolith if present.
6. Complications: Describe a visible wall defect, collection/abscess, phlegmon, substantial free fluid, peritoneal findings, and ileus.
7. Alternative cause: Review the cecum and terminal ileum, small bowel, urinary tract, pelvis, and other imaged organs for the clinical question.
8. Impression: State the level of certainty and any complication that may affect management in the first sentence.

Complete report framework

Examination: [CT abdomen and pelvis with IV contrast / without IV contrast].
Indication: [Right lower quadrant pain, fever, leukocytosis, or clinical question].
Comparison: [Date / none available].

Technique: [Phase, contrast, and reconstructions]. [Motion or other limitation].

Findings: The appendix is [fully / partly] visualized. It arises from the cecal base and courses [location and course]. Outer-to-outer short-axis diameter is [ ] mm; the wall is [ ]; the lumen contains [ ]. Periappendiceal fat is [ ]. Appendicolith [absent / location]. Extraluminal gas [ ]. Collection or phlegmon [ ]. Free fluid and adjacent bowel/cecal findings [ ]. [Important alternative finding or structure outside the field].

Impression:
1. [Findings support appendicitis / normal appendix / equivocal appearance with stated limit of certainty].
2. [Abscess, phlegmon, evidence of perforation, or alternative diagnosis, if present].

Example 1 — normal visualized appendix

Fictional case. A normal report applies when the appendix has been adequately assessed.

Examination: CT abdomen and pelvis with IV contrast.
Indication: Right lower quadrant pain; suspected acute appendicitis.
Comparison: None available.

Technique: Portal venous phase CT of the abdomen and pelvis. Axial images and coronal and sagittal reformations reviewed. Diagnostic image quality.

Findings: The appendix is visualized throughout and measures 5 mm in outer-to-outer diameter. No wall thickening or abnormal enhancement. No periappendiceal fat stranding, appendicolith, or collection. The terminal ileum and cecum are unremarkable. No acute finding in the other imaged structures.

Impression:
1. No CT evidence of acute appendicitis.

If the appendix is not fully or adequately seen, do not copy this conclusion. Describe the visible segment, the presence or absence of secondary inflammation, and the limitation.

Example 2 — borderline calibre without secondary inflammation

Fictional case. This illustrates a borderline enlarged appendix without other supportive findings.

Examination: CT abdomen and pelvis with IV contrast.
Indication: Right lower quadrant pain.
Comparison: None available.

Technique: Portal venous phase contrast-enhanced CT abdomen and pelvis; coronal and sagittal reformations reviewed.

Findings: The appendix is partly visualized and measures approximately 7 mm in outer-to-outer diameter in the visible segment. No convincing wall thickening or abnormal enhancement. No periappendiceal fat stranding, appendicolith, collection, or extraluminal gas. No substantial inflammatory change in the cecum or terminal ileum.

Impression:
1. Partly visualized appendix with borderline calibre and no convincing secondary CT signs of inflammation. The findings alone are not diagnostic of appendicitis. Correlation with clinical and imaging findings is appropriate if concern persists.

Nonvisualization or partial visualization does not have one meaning in every case. State whether secondary inflammatory findings are present; avoid definitive exclusion when the examination is limited. Do not turn diameter into a positive or negative diagnosis by itself.

Example 3 — appendicitis with abscess

Fictional case. Measurements and findings are educational examples and do not represent a real patient.

Examination: CT abdomen and pelvis with IV contrast.
Indication: Four days of right lower quadrant pain and fever.
Comparison: None available.

Technique: Portal venous phase CT abdomen and pelvis; axial, coronal, and sagittal images reviewed.

Findings: The appendix extends retrocecally from the cecal base and measures up to 12 mm in diameter. Its wall is thickened and avidly enhancing, with marked adjacent fat stranding. A 3.2 cm rim-enhancing collection lies next to the appendiceal tip, with localized extraluminal gas. Mild reactive thickening at the cecal base. No diffuse pneumoperitoneum or bowel obstruction.

Impression:
1. Acute appendicitis with a 3.2 cm periappendiceal abscess and localized extraluminal gas, supporting complicated/perforated appendicitis.
2. No diffuse pneumoperitoneum.

Report the collection’s dimensions and location relative to the appendix when relevant to surgical or interventional planning. If a small extraluminal gas focus or wall irregularity is present, describe what is seen; do not overstate certainty when a perforation site is not directly demonstrated.

Common impression pitfalls

• Treating diameter as the only finding: Normal and inflamed appendiceal calibre can overlap. Interpret size with the wall and adjacent tissues.
• Equating an appendicolith with appendicitis: An appendicolith by itself, without surrounding inflammation, does not establish acute appendicitis.
• Calling a nonvisualized appendix normal: Document why it is not seen, what segment is visible, and whether secondary signs are present.
• Looking for perforation only as free gas: A wall defect or gas may not be visible in every case. Also assess for a collection, phlegmon, extraluminal appendicolith, and surrounding inflammation.
• Omitting alternatives: Right lower quadrant CT may show bowel, urinary, or gynecologic causes other than appendicitis.
• Assigning clinical severity from the image alone: Describe morphology clearly; overall clinical severity cannot be inferred from CT alone.

Quick pre-sign-off check

Is the extent of appendix visualization clear? Are calibre and wall findings described? Were surrounding fat, appendicolith, extraluminal gas, and collection assessed separately? Were alternative diagnoses considered? Does the impression express uncertainty and complications at the right level?

References

• American College of Radiology. ACR Appropriateness Criteria®: Right Lower Quadrant Pain (Revised 2022) — abdominopelvic imaging for suspected appendicitis and alternative diagnoses. Guideline (opens in a new tab)
• World Society of Emergency Surgery. Diagnosis and Treatment of Acute Appendicitis: 2025 Edition of the WSES Jerusalem Guidelines. JAMA Surgery. 2026;161(3):283–295. doi:10.1001/jamasurg.2025.6218. PubMed (opens in a new tab)
• Leeuwenburgh MMN, et al. A Novel Reporting System to Improve Accuracy in Appendicitis Imaging. Radiology. 2015. Article (opens in a new tab)
• Nikolaidis P, et al. The nonvisualized appendix: incidence of acute appendicitis when secondary inflammatory changes are absent. AJR Am J Roentgenol. 2004;183:889–892. PubMed (opens in a new tab)

Educational note: All cases are fictional and contain no patient data. This article does not replace patient-specific interpretation, current local protocols, or specialist judgment.